1. Field of the Invention
The present invention relates to a disc drive for playing back or recording and playing back a disc such as an optical disc or the like.
2. Description of the Prior Art
One example of a disc drive for playing back an optical disc such as a CD-ROM or the like is disclosed in an application (Japanese Utility Model Application No. HEI-5-69414). FIG. 1 is an exploded perspective view which shows the structure of the disc drive of this application.
As shown in this drawing, a disc drive 1B is constructed from a main body 2, a disc tray 5 which moves backwards and forwards with respect to the main body 2 to enable the disc tray 5 to be insertable into and ejectable out of the main body 2, a circuit substrate assembly 12 arranged below the main body 2, and a casing 10 which houses all these elements.
The casing 10 is constructed from a bottom plate 11 and a case 14 which covers the top of the main body 2. The bottom plate 11 and the case 14 are made from metal plates which have undergone a bending process to form a desired shape.
The case 14 is constructed from a top plate 14a, side walls 14b, 14c which face each other through the main body 2, a rear wall 14d which connects the rear edges of the side walls 14b, 14c, and a front plate portion 14e at the front thereof.
Formed in the front plate 14e of the case 14 is an aperture 141 to allow the disc tray 5 to be passed therethrough. A front panel 13 having an aperture 13a corresponding to the aperture 141 is mounted to the front plate 14e via a cushioning member frame 15.
The main body 2 includes a roughly container-shaped chassis 20 which is provided with a mechanism unit 22 and a displacement mechanism (ascending/descending mechanism) 30. The mechanism unit 22 is arranged within a concave portion formed in the bottom portion 20a of the chassis 20. Further, the main body 2 is fixed to the bottom plate 11 and the case 14 by means of screws 17.
The mechanism unit 22 includes a base 23 which is provided with a spindle motor 25 for rotating a turntable, a turntable 26 which is fixed to a rotation axis of the spindle motor 25, an optical head (optical pick-up) 27, and an optical head moving mechanism 28. Further, a rear end portion (toward the back of the main body 2) of the base 23 is supported by an insulator 29 to enable the base 23 to be freely pivotal with respect to the chassis 20.
The displacement mechanism 30 is constructed from a motor 31 provided at a front portion of the chassis 20, a rotational speed reduction mechanism 32 for reducing the rotational speed of the motor 31, a cam wheel (ascending/descending gear) 33 which is rotated via the rotational speed reduction mechanism 32, and a base ascending/descending member (not shown in the drawing) which is displaced (pivoted) in accordance with the rotation of the cam wheel 33.
The cam wheel 33 includes a lower gear 33a which meshes with a pinion gear of the rotational speed reduction mechanism 32, and an upper gear 33b which meshes with a rack gear (not shown in the drawing) formed on the rear surface of the disc tray 5 in the forward and backward direction thereof. Further, a circumferential cam groove is formed in the outer circumference of the axle portion between the gears 33a, 33b. This cam groove receives a protruding follower (not shown in the drawing) formed on the base ascending/descending member. Consequently, as the cam wheel is rotated, the follower and the base ascending/descending member are displaced, and this causes the base 23 to pivot; namely, the front portion of the base 23 is pivotally moved up or down between a raised position and a lower position.
Further, a disc clamp 38 is provided on a top plate 14a of the casing 10 in a manner that enables the disc clamp 38 to rotate with respect to the top plate 14. Further, the disc clamp 38 is adapted to attach to the permanent magnet provided in the turntable 26 by the attracting force thereof, whereby the optical disc 3 can be held between the turntable 26 and the disc clamp 38.
The disc tray 5 includes a shallow concave disc supporting portion 5a for supporting an optical disc 3, and the rack gear is formed on the rear surface thereof (not shown in the drawing) which meshes with the upper gear 33b of the cam wheel 33. Consequently, as the cam wheel 33 is rotated, the disk tray 5 is moved forward or backward with respect to the chassis 20 between a disc unloading position (eject position) and a disc loaded position (playback position).
When the disc drive 1B is not in use, the disc tray 5 is housed within the casing 10 (at the disk loaded position/playback position). In this state, if an eject operation is carried out, the motor 31 is rotated in a prescribed direction, whereby the cam wheel 33 is rotated in a counterclockwise direction via the rotational speed reduction mechanism 32. This rotation of the cam wheel 33 causes the disc tray 5 to move forward and protrude to a position (the disc unloading position) outside the casing 10 through the apertures 141, 16a.
In this state, a disc 3 is loaded into the disc loading portion 5a of the disc tray 5, and a loading operation is carried out, whereby the motor 31 is rotated in the opposite direction, and this causes the cam wheel 33 to rotate in the opposite direction via the rotational speed reduction mechanism 32. Consequently, the disc tray 5 is moved toward the back of the disc drive, through the apertures 141, 13a, to the disc loaded position. In this way, the loaded optical disc 3 which is placed at a prescribed position on the disc tray 5 is also transported to the disc loaded position of the main body 2.
Further, when the cam wheel 33 begins to rotate in the opposite direction, the follower of the base ascending/descending member moves along the cam groove, and the center of the disc 3 approaches the central portion of the turntable 26, at which time the follower and the base ascending/descending member are displaced, and the front portion of the base 23 pivots about the position of the insulator 29 to go from a lower position to a supported higher position, whereby the base 23 is placed in a roughly horizontal state.
In this way, the center portion (center hub portion) of the turntable 26 is fitted into a center hole 3a of the optical disc 3, and as the center portion of the optical disc is supported in this way, the disc clamp 38 is magnetically stuck to the turntable 26, with the optical disc 3 being held between the turntable 26 and the disc clamp 38. In this state, the spindle motor 25 is operated to rotate the optical disc 3 at a predetermined rotational speed, and then the information recorded on the optical disc 3 is played back using the optical pick-up 27.
If an eject operation is carried out while the rotation of the optical disc 3 is stopped, the operations of each mechanism of the disc drive 1B described above are carried out in reverse order and direction, thereby the disc clamp 38 being released and thereby the optical disc 3 supported on the disc tray 5 being ejected.
In the disc drive 1B having the construction described above, it is possible to smoothly move the disc tray 5 and raise and lower the mechanism unit 22, and it is also possible to reliably and accurately carry out all the basic required operations, such as disc loading, disc recording/playback and disc ejection.
However, in recent years, it has become necessary to reduce the cost of this type of disc drive in order to lower the overall cost of the computer itself. As a result, there is a need for a disc drive having a simpler construction made from fewer parts which can be assembled in fewer steps, but this is very difficult to achieve with the prior art disc drive described above due to the use of the relatively complex construction of the cam wheel, base ascending/descending member and the like.
Further, in recent years, disc drives have been developed to rotate a disc at high speeds, such 8 times speed, 12 times speed and the like, however this has created problems. Namely, when a disc is rotated at such a high speed, the dimensional error and the deviation of the center of mass of the disc will create an eccentric rotation which can generate vibration. If thus generated vibration is transmitted to the chassis and the casing, such transmitted vibration can cause noise to be emitted from the disc drive. Accordingly, in disc drives which rotate a disc at high speed, there is a need to prevent the transmission of vibrations generated by the rotation of the disc.